From the blog Today I Found Out, here's something I bet you didn't know about 7-11's Double Big Gulp:

Today I found out that the 7-11 Double Big Gulp holds about twice the amount of fluid than the average adult human’s stomach. The average adult human’s stomach can hold reasonably comfortably approximately 32 ounces at any given time. The Double Big Gulp holds about 64 ounces of soda or Slurpee.